It has been proposed that a cell can reprogram and express genes hitherto inactive only after a quantal mitosis thereby suggesting a causal correlation between DNA synthesis/cell division and reprogramming of the genome. Holometablous insects (Galleria and Tenebrio) are suitable organisms to test this hypothesis. Integument from a penultimate instar Galleria larva can secrete either a larval cuticle or pupal cuticle depending on the hormonal milieu in which it is implanted. DNA synthesis in the implanted epidermal cells, as monitored by autoradiographic analysis of incorporation of 3H thymidine and 3H cytosine show that these cells reprogram their genome without any intervening DNA synthesis. Galleria pupal integument when implanted into a normal or JH-treated pupae secrete adult and pupal cuticles respectively. Our autoradiographic studies show that during pupal-adult transformation, the implanted epidermal cells incorporate 3H thymidine. Since Galleria adult integument has scales and because scale formation requires two successive cell divisions, we are examining whether pupal-adult transformation in a colepteran insect, Tenebrio, (which has no scales) is also accompanied by cell divisions. We are also investigating the effect of mitotic inhibitors e.g. mitomycin (that suppress scale formation), on the expression of surface patterns, pigmentation and tanning characters of the adult cuticle.